1. Field of the Invention
The present invention relates to a color matching process.
2. Description of the Related Art
In color matching between devices of different types, generally, a color appearance model such as CIECAM02 which is recommended by the Commission Internationale de l'Eclairage (CIE) is used. A color appearance model predicts color appearances in viewing environments having different characteristics while considering chromatic adaptation.
The human visual system has a function to change its sensitivity so as to adapt to a new environment. For example, when a person moves from a room illuminated by a fluorescent lamp of a daylight color to a room illuminated by an incandescent lamp, he or she initially feels the illumination light as yellowish. After a while, however, he or she does not feel the yellowishness. This is because the visual sense adapts to the illumination light, that is, correction action of the visual system is occurred. This is called chromatic adaptation.
Adaptation of the visual system cannot completely cancel the change of illumination light. Even when the visual sense chromatically adapts to the illumination light sufficiently, it does not perceive the color of the illumination light as white. This is called incomplete adaptation.
Chromatic adaptation and incomplete adaptation also occur when viewing a monitor. For example, when viewing a monitor whose white point has a high color temperature, a person initially feels it as bluish, but less bluish after a while (chromatic adaptation). However, the bluishness cannot be completely canceled (incomplete adaptation).
CIECAM02 uses equal energy white (X=Y=Z=100) in a color prediction process to perform correction while considering incomplete adaptation. Theoretically, equal energy white is regarded to be perceived as white by a human. However, since the color temperature of equal energy white is about 5,460K, the human visual system perceives it as a considerably yellowish color. For this reason, incomplete adaptation cannot be accurately predicted.
When a display image on a monitor and an output image (printed material) from a printer are placed side by side and viewed, the visual system tries to adapt to both of the white color of the monitor and that of the viewing light obtained from the ambient light reflected from the printed material. Accordingly, by using an adaptation white point considering partial adaptation, the color matching accuracy can be improved.
In Japanese Patent Laid-Open No. 9-093451, a partial adaptation white color for a monitor is obtained from the monitor white color and illumination light white color. On the other hand, as an adaptation white color for a printer, a white color without considering partial adaptation is used. That is, the partial adaptation model in Japanese Patent Laid-Open No. 9-093451 considers the influence of the illumination light upon viewing the monitor, but does not consider that of the monitor upon viewing the printed material. As a result, color matching with a high accuracy cannot be implemented between a monitor and printer.